TD5 performance chip upgrade

I have seen an advert for a TD5 chip upgrade that promises 40bhp and an extra 60lb of torque. I realise that the turbo boost is increased, with corresponding fueling adjustments, but are there any downsides to doing this? They even claim an economy improvement of 15%....the company is Froggatts of Macclesfield, a long established Land Rover specialist.

Td5 is a strong lump and will cope ok with tuning.

I've driven a 90 which had a chip, bigger turbo and intercooler, it was f***ing quick!!!!